Ocean Currents/Transcript
Transcript A boy, Tim, and a robot, Moby, face each other in a small boat. TIM: I spy, with my little eye, something that's blue. MOBY: Beep. TIM: Yep, the ocean. You win again. This game is getting kind of boring. A bottle with a letter inside of it floats by the boat. TIM: Hey, a message in a bottle. Tim retrieves the bottle and reads from the typed letter. TIM: Dear Tim and Moby, My mom said you might get this message if I put it in the ocean. How can this happen? From, Vivian TIM: Vivian, does your mom know that we got shipwrecked? And that we've been drifting around aimlessly for a week? Please, tell your mom to call the coast guard. I'm extremely hungry out here. MOBY: Beep. TIM: What do you mean she doesn't know? MOBY: Beep. TIM: She's asking about ocean currents? Oh, all right. The waters off the world's oceans are always on the move. Ocean currents help ships, animals, and bottles move around the globe. An animation shows a ship, sea turtle, whale, and bottle moving in the ocean. TIM: The ocean can be thousands of meters deep. But surface currents only affect the uppermost 100 or 200 meters of water. An animation shows the surface currents as Tim describes. TIM: Fortunately, I brought my map of ocean surface currents with me. Tim unfolds a map. MOBY: Beep. TIM: If you look closely, you'll see that the currents actually move in large circular patterns called gyres. And each gyre is bordered by one or more continents. A world map shows the location of the gyres in the oceans. TIM: Surface currents are mainly caused by wind. You might not know this, but some winds blow across the ocean in the same direction all year round! An animation shows the direction of the wind in different oceans. TIM: The rotation of the earth causes the winds to deflect off to the right in the Northern Hemisphere, and deflect off to the left in the Southern Hemisphere. This is called the Coriolis effect. That makes gyres rotate clockwise above the equator, and counter-clockwise below it. Surface currents have a major effect on climate and weather conditions. An animated popup shows the earth rotating. The world map shows the direction the gyres rotate in the Northern and Southern Hemispheres as Tim describes. TIM: If you look at the map, you'll see that Paris, France, is at about the same latitude as Montreal, Canada. But winters in Paris are a heck of a lot nicer than winters in Montreal. A map shows that Paris, France, and Montreal, Canada, are on the same latitude. Side by side images show a woman in Montreal bundled up in a heavy parka with snow falling and a man in Paris wearing an open jacket under a cloudy sky. TIM: Parisians can thank a current called the Gulf Stream for that: it delivers warm water from the tropics to Western Europe! An animated world map shows how the gulf stream directs warm water from the tropics toward Europe. TIM: In the North Atlantic, the Gulf Stream radiates heat into the atmosphere. That's why the winters are warmer in France! An animation shows how the gulf stream reflects the heat from the sun and turns it into warm air. TIM: Currents can make for colder climates, too. Hawaii is located in the tropics, but its climate is slightly cooler than other tropical locations, since the California Current, brings cool water south. A map of the United States and the Pacific Ocean shows how the direction of the California Current circulates cooler air around the Hawaiian islands. MOBY: Beep. TIM: Yeah, it’d be nice if we drifted ashore in Hawaii. Anyway, deep beneath the ocean surface, there's another current system. It's not powered by wind at all, but by temperature and density. A world map shows a system of currents looping across the oceans. TIM: Remember the Gulf Stream? MOBY: Beep. TIM: What are you talking about? I just described it like, 30 seconds ago. Well like I said, in the North Atlantic, the warm waters of the Gulf Stream radiate heat into the atmosphere. A gulf stream animation shows the warm air moving across the Atlantic Ocean. TIM: This loss of energy causes the water to cool off, until it's almost freezing. Cold water is denser than warm water, so the surface water soon begins sinking. Millions of liters of water sink in the North Atlantic every day, but they can't just pile up there. They have to flow somewhere else. An animation shows cold, dense water sinking to the bottom of the North Atlantic. TIM: So when the cold water gets two or three kilometers down, it starts moving south! It flows all the way to Antarctica, then starts flowing north again. In the Pacific, the water starts warming up and returns to the surface. It flows back into the Atlantic Ocean where it joins up, once again, with the Gulf Stream. And once the Gulf Stream waters reach the North Atlantic, they lose heat and sink, and the whole process starts over again! Because this current system loops all the way around the globe, it's sometimes called the global conveyor belt. The belt moves very slowly: it can take a thousand years for water to make the full circuit around the earth! An animation traces the movement of the cold water south to Antarctica. Then the water flows back north where it warms up again. An arrow shows the direction of the warm and cold currents as they loop around like a conveyor belt as Tim describes. Moby points at something. MOBY: Beep. TIM: Land! Moby, we're saved! Tim and Moby step onto the land and look around. TIM: Woo-hoo! We made it! The land is completely dry and barren. TIM: Oh, drat. Tim sighs. Category:BrainPOP Transcripts